1. Field of the Invention
The present invention relates in general to an erosion control system for reducing erosion and, more particularly, to a system for reducing erosion of erosion susceptible areas in flowing effluent environments.
2. Description of the Prior Art
The Clean Water Act and subsequent legislation requires storm water to be discharged in a non-erosive manner. Unfortunately, storm water pipe outlets and the like used to divert water runoff are highly erosive at their outlets as the result of velocity and shear force problems associated with the funneling of water toward a narrow outlet. Erosion control associated with such Outlets involves economic, physical and logistical problems. Traditionally, storm water is transported from a street or parking lot in a storm water pipe to a conveyance, such as a stream or river. Storm water may also be drained from a permanent structure, like a parking lot, at designated outlets where it flows overland and naturally dissipates. The soil area adjacent such discharge points is highly susceptible to severe erosion associated with discharging water.
The energy of water discharging from such outlets varies with the velocity, shear force and volume of the effluent. Water 25 centimeters deep, flowing rapidly, is much more erosive and destructive than water 8 centimeters deep, flowing at the same rate. Accordingly, allowing runoff water to spread out is an effective means to counteract funneling of discharge water, dissipating both velocity and shear force without mechanical input. Conversely, squeezing water raises its height and increases its hydraulic pressure. This increase in hydraulic pressure results in increased shear force which, in turn, leads to increased erosion. Unfortunately, the factors associated with diverting water, namely collecting water from a relatively large area and funneling it to a very small area, using hard, smooth surfaces, cannot help but magnify the weight, velocity and shear force of the water at the discharge point.
Traditionally, at such discharge points, material, such as rip rap, is added. Such installation of various sized rocks, stacked in a concave manner to funnel water, may be used to reduce erosion, but is very expensive and time consuming to install. Alternatively, concrete blankets (flat soft material filled with concrete or concrete blocks held together with steel cables), or concrete slabs may be used to control erosion at discharge points. These products, and other similar products, are referred to as “hard armor.” Hard armor often dissipates water energy and protects the soil therebeneath from eroding away and polluting natural resources. One drawback associated with hard armor is the requirement of very large equipment needed to install the hard armor. Additionally, a significant volume of material must be freighted to the site and a large amount of preparatory work is required before installing the hard armor.
While hard armor is useful for dissipating velocity and countering shear forces associated with runoff water, poor installation often allows the water to splash or divert out of the designated channel, many times leading to the erosion and washout of the hard armor installation itself. While concrete blankets are better able to withstand velocity and shear forces, they do little to inhibit the velocity and, therefore, the destructive force of water runoff. Another drawback associated with hard armor is that it typically lacks aesthetics associated with other forms of erosion control.
Recently, the industry has developed blanket-type products called turf reinforcement mats to convey water and withstand designated loads. While such turf reinforcement mats do little to reduce or mechanically dissipate the energy of runoff water energy themselves, their installation allows for the growth of vegetation which, in turn, mechanically reduces energy associated with runoff water. Such blankets are typically three-dimensional, flexible mats constructed of plastic webbing. The open weave of such mats allows vegetation to grow up therethrough. The combination of the mechanical stable structure and open weave design results in a significant synergistic effect, with the capacity to carry much greater velocity and sheet force load because roots and stems associated with the upgrowing vegetation are reinforced by the mat.
It is also known in the art to provide an erosion control mat as described in U.S. Letters Pat. No. 6,951,438 to reduce erosion. The erosion control mat is more rigid than turf reinforcement mats. Unlike hard armor, the erosion control mats allow for vegetative growth therethrough. Although turf reinforcement mats and erosion control mats have numerous advantages over the prior art in terms of reducing erosion, it is often difficult to securely mount these types of mats in an erosion susceptible area. While the mats may obviously be secured into concrete blankets, if it is desired to secure the mats directly to the soil, complex and expensive anchoring systems requiring specialized tools and multiple installers are typically required. One method of installation involves securing a pivoting anchor to a cable and driving the anchor and cable through the mat into the soil. The cable is then lifted upward to pivot and lock the anchor. One installer thereafter pulls upward on the cable, while a second installer swages a bead to the cable to prevent the mat from becoming dislodged from the ground. Although this system works reasonably well for securing mats to the ground, the system involves several drawbacks.
First, the system typically requires multiple installers, one to generate sufficient upward force to eliminate any slack in the cable, while a second installer crimps the bead to the cable. Another drawback associated with the prior art is that the system typically involves a complex securement of the cable to the anchor. This requires the anchor to be associated with a predetermined length of cable, which must be cut to size with the remainder discarded. This leads to undesired waste and severely limits the use of the system in areas where a securement lower than the predetermined length of the cable is desired.
Another drawback associated with prior art is the lack of resiliency associated with the cable. Even using multiple installers, the system typically does not provide significant bias of the mat into the ground. As the installation system typically results in at least a small amount of “play” between the mat and the ground, effluent can often move underneath the mat, causing undesired erosion and additional play between the mat and the ground. Play is a particular problem in continuous water flow environments, such as creek beds and large flow and pressure environments such as drainage ditches. If the play becomes substantial enough, the anchor can become dislodged, allowing the mat to move away from the erosion susceptible surface, thereby defeating the purpose of the mat.
Another drawback associated with the prior art is the weight of the prior art anchoring systems. While the weight of one anchor system is of only marginal consequence, the cost of transporting and moving a large number of anchors makes the use of heavy anchors and cables undesirable. Still another drawback associated with the prior art is the difficulty in removing the anchor system if it is desired to remove the mat. Typically, removal requires multiple installers with the first installer pulling upward on the bead sufficiently to allow the second installer to move bolt cutters between the bead and the mat. The difficulties encountered in the prior art discussed hereinabove are substantially eliminated by the present invention.